The present invention relates to an input/output system having an output device and an input device and, for example, can be suitably used for an input/output system in which an input device determines validity of data input from an output device.
In recent years, the number of in-vehicle MCUs (Micro Control Units) mounted in vehicles and having an interface function for inputting image data is increasing. For example, a dashboard MCU mounted in a dashboard of a vehicle performs operation of inputting image data of the periphery of the vehicle captured by cameras and displaying the input image data to a dashboard panel. Consequently, it is an important function for an in-vehicle MCU to assure validity of input data also from the viewpoint of safety, and the measure for it is an urgent task.
Hereinafter, three related arts regarding assurance of validity of data which is input to an MCU will be described.
(1) AMI Coding (Alternative Mark Inversion Code) Method
The AMI coding method is one of coding methods used for digital communication. The AMI code is a code expressing 0 when the logical state “0” is generated in data and expressing a positive or negative polarity code when the logical state “1” is generated. In the AMI code, each time the logical state “1” is generated in data, the positive and negative polarity codes are alternately repeated. Consequently, the data waveform includes little DC components, is close to an AC signal, and is unsusceptible to noise or the like, so that stable data transmission can be performed.
(2) ECC (Error Correction Code)
The error correction code is a code added to data so that a receiver side can detect and correct an error which occurs at the time of recording/transmitting data (refer to, for example, patent literature 1). The error correction code is calculated from original data on the basis of a predetermined procedure and recorded/transmitted together with the original data.
(3) Multiplexing of Data Lines
Multiplexing of data lines denotes multiplexing of data lines between a transmitter side and a receiver side. For example, in the case of duplicating data lines, the transmitter side transmits the same data by two data lines. The receiver side determines whether the data is valid or not by comparing the data transmitted by the two data lines.